Landmarking protocol 3d3 (LM3d3) represents a significant advancement from LM3d1 (Selden Jr., Dockall, and Dubied 2020) and LM3d2 protocols that were developed to analyse Gahagan bifaces, which evolved from a 2D study (Selden Jr., Dockall, and Shafer 2018). Like LM3d1 and LM3d2, LM3d3 uses the mesh topology as the foundation for additional components of reference geometry, further expanding upon the previous landmarking protocols. The result is a landmarking protocol that provides for the improved characterisation of whole-object morphology, which can also be subset to explore morphological variation in plan, profile, and cross-section morphology. It also provides those data points needed to investigate questions of directional asymmetry, differences in front/back morphology, and morphological integration between blade and basal morphology.
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Landmarks from LM3d1 serve as the basis for LM3d3.
Like its’ predecessors, LM3d3 was initially designed using the digit3DLand package in R. When the draft protocol was complete, it shifted to Geomagic Design X (Build Version 2020.0.1 [Build Number: 30]), where the workflow was modified to include those elements of reference geometry that articulate with the specific design attributes of each point.
The goal of this effort was to increase both the precision and rigour of the study by including the Z-dimension to capture morphological characteristics associated with axial twisting introduced by knappers through the practice of beveling (LM3d1) (Selden Jr., Dockall, and Dubied 2020). The addition of cross-sections was needed to better characterise whole-object morphology, providing for the possibility of subsampling the landmarks to explore the contribution of a specific cross-section or profile (LM3d2). LM3d3 includes an additional cross section at the blade/base transition, allowing for tests of morphological integration. While true that some landmarking protocols can be—–and often are—–recycled as new specimens are added, this particular research programme endeavours to achieve ever-greater accuracy and precision in each analytical iteration.
Note: this landmarking protocol was developed prior to running auto3dgm, and details the procedure for applying landmarks and equidistant semilandmarks; however, it may not reflect their actual placement on this specimen.
A suite of visual aids was created a means of visualising the various hypotheses that this landmarking protocol will be used to test. The visual representation of the following hypotheses were produced for my own reference, and used to critically assess the utility of the semilandmarks employed in the landmarking protocol. All hypotheses tested for this study will enlist the same sample of Dalton projectile points.
Hypothesis 1 will test whether there is a difference in morphology for Dalton points found in and out of the heartland.
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Hypothesis 1 considers whether Dalton points discovered in and out of the Heartland differ in morphology.
Hypothesis 2 will test whether there is a difference in morphology for Dalton points found in the heartland, the interior, and the northern periphery.
knitr::include_graphics('images/dalton-vizhypothesis2.jpg')